HYDROSTATIC HEAD

10,000mm = Suitable for everyday hiking in light rain showers. A good benchmark for a hillwalking waterproof. 20,000mm = Should stand up to heavy and prolonged rain in most conditions. 30,000mm = Waterproof in even the most extreme conditions. Unlikely to leak even at pressure points. However, many brands argue that such a high level of waterproofing is essentially overkill.